on my 50g tank my returnwas half way down in the tank. s to break the syphon i added a t at the top near the overflow. on the topof the t i added a irrigation part that had two nipples that i could attach airlinehose to. when runningthe airline hose fed water intoo the overflow. when turned off it broke the syphon. itwas quiet i didnt hear the sucking sound i hear onmy 90g which i just drilled a hole under the ater linewater line.
here is a picture
